254 RESULTS OF THE METEOHOLOGICAL OBSERVATIONS TAKEN DURING 



marked. Temperature shows a minimum at 5 a.m. falling 0°'6 below the mean of the 

 clay, and a maximum at 1 and 2 p.m. exceeding the mean of the day by 0°"7, 

 there being thus a difference of 1°'3 between the warmest and coldest hours. The 

 diurnal variation in the amount of cloud is somewhat irregular, but, speaking broadly, 

 there is an excess from 8 a.m. to 8 p.m., while during the other hours cloud is in defect. 

 The wind force is greatest during the night and least during the day, being highest 

 from 10 P.M. to 2 a.m. and lowest from 8 a.m. to 2 p.m. The daily range in relative 

 humidity is well shown, the maximum being recorded at 5 a.m. and the minimum at 

 noon and 2 P.M. As there is no variation in the vapour tension, the values are not given. 

 During the second Antarctic cruise of the "Scotia" the conditions affectino- the 

 diurnal range of the elements differed consideraljly from time to time, as the rauge in 

 latitude was very great. I have accordingly computed mean hourly values for different 

 groups of days, in which the mean position varied from over 72° S. to as low as 40° S., 

 taking out the departure of each hour from the daily mean, and further smoothing the 

 results by continuous three-hour groups in order to eliminate the more pronounced 

 irregularities due to the shortness of the periods. In one case, viz., in the barometric 

 means for the ten days 11 th to 20th April, it was necessary to discard the observations 

 for 15th April, as a remarkably deep V-shaped depression occurred on the afternoon of 

 that day which enormously intensified the afternoon minimum of pressure for the 

 ten-day period. The values given for this element are thus the mean of nine days. 



It is of interest to note the values for the period 11th to 20th March, during which the 

 continental inilueuce exerted by the proximity of Coats' Land is clearly shown. This is 

 most pronounced in the case of the temperature curve, the difference between the smoothed 

 hourly values being 3°'3, or nearly twice as great as during any other period discussed 

 and three times greater than during the preceding ten-day peiiod. The pressure curve 

 strongly resembles that of the South Orkneys in the long-drawn-out morning minimum 

 and the veiy pronounced evening maximum, which are so characteristic of the Scotia 

 Bay Station at a time when these islands^ owing to the freezing up of the sea to the 

 south, are essentially subject to conditions of a continental character. The diurnal range 

 of cloud and wind force is also very pronounced, and lioth are of the type associated 

 with extensive land masses. 



In the South Atlantic, during Ai)ril 1904, the double maximum and minimum of 

 pressure is well shown. The morning minimum occurs at 5 a.m., after which pressure 

 rises till 11 a.m., the afternoon minimum occurs at 5 p.m., and the evening maximum 

 at 11 P.M. Temperature is above the mean from 10 a.m. to 8 p.m., the minimum 

 occurring about 6 a.m. and the maximum at 1 and 2 p.m. The wind force is least about 

 7 A.M. and greatest at 10 p.m. Eelative humidity shows a double period, the principal 

 minimum taking place at 11 a.m. and a secondary at fi p.m., while the maximum is 

 reached at 10 P.M., with another small maximum about 4 P.M. The vapour pressure 

 shows a well-jjronounced morning minimum and a small secondary minimum at 6 p.m., 

 while there are two maxima, one about 3 p.m. and the other at 10 p.m. {See Plate V.) 



